[Lldb-commits] [lldb] [lldb/aarch64] Fix unwinding when signal interrupts a leaf function (PR #91321)
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lldb-commits at lists.llvm.org
Tue May 7 05:01:18 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-lldb
Author: Pavel Labath (labath)
<details>
<summary>Changes</summary>
A leaf function may not store the link register to stack, but we it can still end up being a non-zero frame if it gets interrupted by a signal. Currently, we were unable to unwind past this function because we could not read the link register value.
To make this work, this patch:
- changes the function-entry unwind plan to include the `fp|lr = <same>` rules. This in turn necessitated an adjustment in the generic instruction emulation logic to ensure that `lr=[sp-X]` can override the `<same>` rule.
- allows the `<same>` rule for pc and lr in all `m_all_registers_available` frames (and not just frame zero).
The test verifies that we can unwind in a situation like this, and that the backtrace matches the one we computed before getting a signal.
---
Full diff: https://github.com/llvm/llvm-project/pull/91321.diff
6 Files Affected:
- (modified) lldb/source/Plugins/Instruction/ARM64/EmulateInstructionARM64.cpp (+2)
- (modified) lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp (+1-3)
- (modified) lldb/source/Target/RegisterContextUnwind.cpp (+3-3)
- (added) lldb/test/Shell/Unwind/Inputs/signal-in-leaf-function-aarch64.c (+15)
- (added) lldb/test/Shell/Unwind/signal-in-leaf-function-aarch64.test (+24)
- (modified) lldb/unittests/UnwindAssembly/ARM64/TestArm64InstEmulation.cpp (+20-4)
``````````diff
diff --git a/lldb/source/Plugins/Instruction/ARM64/EmulateInstructionARM64.cpp b/lldb/source/Plugins/Instruction/ARM64/EmulateInstructionARM64.cpp
index 6ca4fb052457e..62ecac3e0831d 100644
--- a/lldb/source/Plugins/Instruction/ARM64/EmulateInstructionARM64.cpp
+++ b/lldb/source/Plugins/Instruction/ARM64/EmulateInstructionARM64.cpp
@@ -444,6 +444,8 @@ bool EmulateInstructionARM64::CreateFunctionEntryUnwind(
// Our previous Call Frame Address is the stack pointer
row->GetCFAValue().SetIsRegisterPlusOffset(gpr_sp_arm64, 0);
+ row->SetRegisterLocationToSame(gpr_lr_arm64, /*must_replace=*/false);
+ row->SetRegisterLocationToSame(gpr_fp_arm64, /*must_replace=*/false);
unwind_plan.AppendRow(row);
unwind_plan.SetSourceName("EmulateInstructionARM64");
diff --git a/lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp b/lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp
index c4a171ec7d01b..49edd40544e32 100644
--- a/lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp
+++ b/lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp
@@ -424,8 +424,6 @@ size_t UnwindAssemblyInstEmulation::WriteMemory(
log->PutString(strm.GetString());
}
- const bool cant_replace = false;
-
switch (context.type) {
default:
case EmulateInstruction::eContextInvalid:
@@ -467,7 +465,7 @@ size_t UnwindAssemblyInstEmulation::WriteMemory(
m_pushed_regs[reg_num] = addr;
const int32_t offset = addr - m_initial_sp;
m_curr_row->SetRegisterLocationToAtCFAPlusOffset(reg_num, offset,
- cant_replace);
+ /*can_replace=*/true);
m_curr_row_modified = true;
}
}
diff --git a/lldb/source/Target/RegisterContextUnwind.cpp b/lldb/source/Target/RegisterContextUnwind.cpp
index 13e101413a477..e2d712cb72eae 100644
--- a/lldb/source/Target/RegisterContextUnwind.cpp
+++ b/lldb/source/Target/RegisterContextUnwind.cpp
@@ -1555,12 +1555,12 @@ RegisterContextUnwind::SavedLocationForRegister(
}
if (unwindplan_regloc.IsSame()) {
- if (!IsFrameZero() &&
+ if (!m_all_registers_available &&
(regnum.GetAsKind(eRegisterKindGeneric) == LLDB_REGNUM_GENERIC_PC ||
regnum.GetAsKind(eRegisterKindGeneric) == LLDB_REGNUM_GENERIC_RA)) {
UnwindLogMsg("register %s (%d) is marked as 'IsSame' - it is a pc or "
- "return address reg on a non-zero frame -- treat as if we "
- "have no information",
+ "return address reg on a frame which does not have all "
+ "registers available -- treat as if we have no information",
regnum.GetName(), regnum.GetAsKind(eRegisterKindLLDB));
return UnwindLLDB::RegisterSearchResult::eRegisterNotFound;
} else {
diff --git a/lldb/test/Shell/Unwind/Inputs/signal-in-leaf-function-aarch64.c b/lldb/test/Shell/Unwind/Inputs/signal-in-leaf-function-aarch64.c
new file mode 100644
index 0000000000000..9a751330623f4
--- /dev/null
+++ b/lldb/test/Shell/Unwind/Inputs/signal-in-leaf-function-aarch64.c
@@ -0,0 +1,15 @@
+#include <signal.h>
+#include <unistd.h>
+
+int __attribute__((naked)) signal_generating_add(int a, int b) {
+ asm("add w0, w1, w0\n\t"
+ "udf #0xdead\n\t"
+ "ret");
+}
+
+void sigill_handler(int) { _exit(0); }
+
+int main() {
+ signal(SIGILL, sigill_handler);
+ return signal_generating_add(42, 47);
+}
diff --git a/lldb/test/Shell/Unwind/signal-in-leaf-function-aarch64.test b/lldb/test/Shell/Unwind/signal-in-leaf-function-aarch64.test
new file mode 100644
index 0000000000000..0580d0cf734ae
--- /dev/null
+++ b/lldb/test/Shell/Unwind/signal-in-leaf-function-aarch64.test
@@ -0,0 +1,24 @@
+# REQUIRES: target-aarch64 && native
+# UNSUPPORTED: system-windows
+
+# RUN: %clang_host %S/Inputs/signal-in-leaf-function-aarch64.c -o %t
+# RUN: %lldb -s %s -o exit %t | FileCheck %s
+
+breakpoint set -n sigill_handler
+# CHECK: Breakpoint 1: where = {{.*}}`sigill_handler
+
+run
+# CHECK: thread #1, {{.*}} stop reason = signal SIGILL
+
+thread backtrace
+# CHECK: frame #0: [[ADD:0x[0-9a-fA-F]*]] {{.*}}`signal_generating_add
+# CHECK: frame #1: [[MAIN:0x[0-9a-fA-F]*]] {{.*}}`main
+
+continue
+# CHECK: thread #1, {{.*}} stop reason = breakpoint 1
+
+thread backtrace
+# CHECK: frame #0: {{.*}}`sigill_handler
+# Unknown number of signal trampoline frames
+# CHECK: frame #{{[0-9]+}}: [[ADD]] {{.*}}`signal_generating_add
+# CHECK: frame #{{[0-9]+}}: [[MAIN]] {{.*}}`main
diff --git a/lldb/unittests/UnwindAssembly/ARM64/TestArm64InstEmulation.cpp b/lldb/unittests/UnwindAssembly/ARM64/TestArm64InstEmulation.cpp
index 80abeb8fae9e5..9303d6f5f3c6e 100644
--- a/lldb/unittests/UnwindAssembly/ARM64/TestArm64InstEmulation.cpp
+++ b/lldb/unittests/UnwindAssembly/ARM64/TestArm64InstEmulation.cpp
@@ -77,7 +77,7 @@ TEST_F(TestArm64InstEmulation, TestSimpleDarwinFunction) {
// UnwindPlan we expect:
- // row[0]: 0: CFA=sp +0 =>
+ // row[0]: 0: CFA=sp +0 => fp= <same> lr= <same>
// row[1]: 4: CFA=sp+16 => fp=[CFA-16] lr=[CFA-8]
// row[2]: 8: CFA=fp+16 => fp=[CFA-16] lr=[CFA-8]
// row[2]: 16: CFA=sp+16 => fp=[CFA-16] lr=[CFA-8]
@@ -88,13 +88,19 @@ TEST_F(TestArm64InstEmulation, TestSimpleDarwinFunction) {
EXPECT_TRUE(engine->GetNonCallSiteUnwindPlanFromAssembly(
sample_range, data, sizeof(data), unwind_plan));
- // CFA=sp +0
+ // CFA=sp +0 => fp= <same> lr= <same>
row_sp = unwind_plan.GetRowForFunctionOffset(0);
EXPECT_EQ(0ull, row_sp->GetOffset());
EXPECT_TRUE(row_sp->GetCFAValue().GetRegisterNumber() == gpr_sp_arm64);
EXPECT_TRUE(row_sp->GetCFAValue().IsRegisterPlusOffset() == true);
EXPECT_EQ(0, row_sp->GetCFAValue().GetOffset());
+ EXPECT_TRUE(row_sp->GetRegisterInfo(gpr_fp_arm64, regloc));
+ EXPECT_TRUE(regloc.IsSame());
+
+ EXPECT_TRUE(row_sp->GetRegisterInfo(gpr_lr_arm64, regloc));
+ EXPECT_TRUE(regloc.IsSame());
+
// CFA=sp+16 => fp=[CFA-16] lr=[CFA-8]
row_sp = unwind_plan.GetRowForFunctionOffset(4);
EXPECT_EQ(4ull, row_sp->GetOffset());
@@ -146,6 +152,12 @@ TEST_F(TestArm64InstEmulation, TestSimpleDarwinFunction) {
EXPECT_TRUE(row_sp->GetCFAValue().GetRegisterNumber() == gpr_sp_arm64);
EXPECT_TRUE(row_sp->GetCFAValue().IsRegisterPlusOffset() == true);
EXPECT_EQ(0, row_sp->GetCFAValue().GetOffset());
+
+ EXPECT_TRUE(row_sp->GetRegisterInfo(gpr_fp_arm64, regloc));
+ EXPECT_TRUE(regloc.IsSame());
+
+ EXPECT_TRUE(row_sp->GetRegisterInfo(gpr_lr_arm64, regloc));
+ EXPECT_TRUE(regloc.IsSame());
}
TEST_F(TestArm64InstEmulation, TestMediumDarwinFunction) {
@@ -381,8 +393,12 @@ TEST_F(TestArm64InstEmulation, TestFramelessThreeEpilogueFunction) {
EXPECT_FALSE(row_sp->GetRegisterInfo(gpr_x26_arm64, regloc));
EXPECT_FALSE(row_sp->GetRegisterInfo(gpr_x27_arm64, regloc));
EXPECT_FALSE(row_sp->GetRegisterInfo(gpr_x28_arm64, regloc));
- EXPECT_FALSE(row_sp->GetRegisterInfo(gpr_fp_arm64, regloc));
- EXPECT_FALSE(row_sp->GetRegisterInfo(gpr_lr_arm64, regloc));
+
+ EXPECT_TRUE(row_sp->GetRegisterInfo(gpr_fp_arm64, regloc));
+ EXPECT_TRUE(regloc.IsSame());
+
+ EXPECT_TRUE(row_sp->GetRegisterInfo(gpr_lr_arm64, regloc));
+ EXPECT_TRUE(regloc.IsSame());
row_sp = unwind_plan.GetRowForFunctionOffset(36);
EXPECT_TRUE(row_sp->GetCFAValue().GetRegisterNumber() == gpr_sp_arm64);
``````````
</details>
https://github.com/llvm/llvm-project/pull/91321
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